The present invention relates to raster scan displays wherein a zoom capability is desired. In particular the present invention relates to a display having a zoom capability that enables the magnification of localized portions of a primary image and the juxtapositioning of the so called zoomed image with respect to the real time image on a common screen.
Prior to the present invention, the typical zoom capability for a radar display required that the entire display image be magnified and displayed. This zoom operation, while permitting viewing the desired image data in greater detail, at the same time, lost substantial portions of the image due to the expansion of the image beyond the boundaries of the fixed display. This occurred because many of the targets that were contained within the fringes of the primary image, upon magnification, fell outside the bounds of the primary image memory and consequently were lost to the image.
The operation of these displays also generally required that the operator first position the display's cursor at a desired location--typically the center of the area to be magnified--and then select the zoom function. The display then adjusted its scale and offset values so as to reposition the selected area in the center of the selected area at the selected magnification factor, but with the attendant problems mentioned above.
The present invention not only permits an operator to similarly select a localized area that he/she desires to zoom, but also to juxtapose the magnified area relative to the unmagnified area, in an uncluttered area of the display, thereby permitting the operator to more closely inspect the zoomed area without losing sight of the rest of the traffic being displayed on the screen. Thus, the operator is able to better distinguish the relative separation between objects that are being tracked when they are relatively close together such as during high traffic situations. Additional operator selected functions that are enabled by the present invention are the operator's ability to position the local zoom data via the use of the joystick, select the frame size within which the zoom data is to appear, control the synthetic persistence of the displayed images, select the magnification or zoom factor desired and provide a multiport local zoom memory design.
The advantages of the present invention will however become more apparent upon a reading of the following description. Further, the operation of the apparatus of the preferred embodiment should become more apparent as well as various equivalent circuitry that can perform the same functions.